Log management and rotation in Jenkins - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to specify the log rotation days in Jenkins pipeline.

Jenkins

pipeline {
  agent any
  options {
    buildDiscarder(logRotator(daysToKeepStr: '[1]'))
  }
  stages {
    stage('Example') {
      steps {
        echo 'Hello World'
      }
    }
  }
}

Drag options to blanks, or click blank then click option'

A30

B10

C60

D90

Attempts:

3 left

💡 Hint

Common Mistakes

Using a string instead of a number

Setting days to 0 which disables retention

The daysToKeepStr option sets how many days Jenkins keeps the logs before deleting them. Here, 30 days is a common default.

2fill in blank

medium

Complete the code to rotate logs based on the number of builds to keep.

Jenkins

pipeline {
  agent any
  options {
    buildDiscarder(logRotator(numToKeepStr: '[1]'))
  }
  stages {
    stage('Build') {
      steps {
        echo 'Building...'
      }
    }
  }
}

Drag options to blanks, or click blank then click option'

A20

B5

C10

D50

Attempts:

3 left

💡 Hint

Common Mistakes

Using a very high number causing disk space issues

Using zero which disables retention

The numToKeepStr option limits how many builds Jenkins keeps logs for. Keeping 5 builds is a common practice to save space.

3fill in blank

hard

Fix the error in the log rotation configuration to correctly discard old builds.

Jenkins

pipeline {
  agent any
  options {
    buildDiscarder(logRotator(numToKeepStr: '[1]', daysToKeepStr: '15'))
  }
  stages {
    stage('Test') {
      steps {
        echo 'Testing...'
      }
    }
  }
}

Drag options to blanks, or click blank then click option'

A-5

B0

C10

Dabc

Attempts:

3 left

💡 Hint

Common Mistakes

Using zero disables retention

Using negative numbers causes errors

Using non-numeric strings causes syntax errors

The numToKeepStr must be a positive number. '10' is valid, while '0', negative numbers, or non-numeric strings cause errors.

4fill in blank

hard

Fill both blanks to configure Jenkins to keep 7 days of logs and 3 builds.

Jenkins

pipeline {
  agent any
  options {
    buildDiscarder(logRotator(daysToKeepStr: '[1]', numToKeepStr: '[2]'))
  }
  stages {
    stage('Deploy') {
      steps {
        echo 'Deploying...'
      }
    }
  }
}

Drag options to blanks, or click blank then click option'

A7

B3

C14

D5

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping the values between days and builds

Using zero or negative numbers

Setting daysToKeepStr to '7' keeps logs for one week, and numToKeepStr to '3' keeps logs for the last three builds.

5fill in blank

hard

Fill all three blanks to configure Jenkins to keep logs for 14 days, 10 builds, and disable artifact retention.

Jenkins

pipeline {
  agent any
  options {
    buildDiscarder(logRotator(daysToKeepStr: '[1]', numToKeepStr: '[2]', artifactDaysToKeepStr: '[3]'))
  }
  stages {
    stage('Package') {
      steps {
        echo 'Packaging...'
      }
    }
  }
}

Drag options to blanks, or click blank then click option'

A14

B10

C0

D7

Attempts:

3 left

💡 Hint

Common Mistakes

Using non-numeric values

Setting artifactDaysToKeepStr to a positive number when disabling is intended

Setting daysToKeepStr to '14' keeps logs for two weeks, numToKeepStr to '10' keeps the last ten builds, and artifactDaysToKeepStr to '0' disables artifact retention.

Practice

1. What is the main purpose of log rotation in Jenkins?

easy

A. To move old logs and save disk space

B. To delete all Jenkins jobs automatically

C. To increase Jenkins build speed

D. To backup Jenkins configuration files

Solution

1. Step 1: Understand what logs do in Jenkins

   Logs record Jenkins activity and can grow large over time.

2. Step 2: Purpose of log rotation

   Log rotation moves or archives old logs to save disk space and keep the system tidy.

3. Final Answer:

   To move old logs and save disk space -> Option A

4. Quick Check:

   Log rotation = save space [OK]

Hint: Log rotation helps keep disk space free by moving old logs [OK]

Common Mistakes:

• Thinking log rotation deletes Jenkins jobs
• Confusing log rotation with backup
• Believing log rotation speeds up builds

2. Which of the following is the correct syntax to configure log rotation using copytruncate in a Linux logrotate config for Jenkins logs?

easy

A. /var/log/jenkins/jenkins.log {
truncatecopy
weekly
rotate 5
}

B. /var/log/jenkins/jenkins.log {
copytruncate
monthly
rotate seven
}

C. /var/log/jenkins/jenkins.log {
copytruncate
daily
rotate 7
}

D. /var/log/jenkins/jenkins.log {
copytruncate
daily
rotate seven
}

Solution

1. Step 1: Identify correct logrotate syntax

   The copytruncate option is valid and used to copy then truncate the log file without stopping Jenkins.

2. Step 2: Check rotation frequency and count

   Using daily and rotate 7 is correct syntax for daily rotation keeping 7 files.

3. Final Answer:

   Correct syntax with copytruncate, daily rotation, and rotate 7 -> Option C

4. Quick Check:

   copytruncate + daily + rotate 7 = correct [OK]

Hint: copytruncate keeps Jenkins running during log rotation [OK]

Common Mistakes:

• Using 'truncatecopy' instead of 'copytruncate'
• Writing 'rotate seven' instead of 'rotate 7'
• Using invalid rotation frequency like 'monthly' with wrong number

3. Given this logrotate config snippet for Jenkins logs:

/var/log/jenkins/jenkins.log {
    copytruncate
    weekly
    rotate 4
}

What will happen after 5 weeks of running this rotation?

medium

A. Jenkins service will stop during log rotation

B. All 5 weeks of logs are kept without deletion

C. Logs are deleted every week without keeping any backups

D. Only the latest 4 weekly logs are kept; older logs are deleted

Solution

1. Step 1: Understand rotate count meaning

   Rotate 4 means keep 4 old log files; older ones get deleted.

2. Step 2: Apply to 5 weeks

   After 5 weeks, the oldest log (week 1) is deleted, keeping only weeks 2-5.

3. Final Answer:

   Only the latest 4 weekly logs are kept; older logs are deleted -> Option D

4. Quick Check:

   rotate 4 means keep 4 logs [OK]

Hint: Rotate number = how many old logs to keep [OK]

Common Mistakes:

• Thinking all logs are kept forever
• Assuming logs delete immediately without backups
• Believing Jenkins stops during copytruncate rotation

4. You configured Jenkins log rotation with copytruncate, but logs keep growing without rotation. What is the most likely cause?

medium

A. The Jenkins service is stopped

B. The logrotate service is not running or not scheduled

C. The copytruncate option is misspelled as copytrunc

D. The log file path is incorrect in the config

Solution

1. Step 1: Check if logrotate runs

   If logrotate is not running or scheduled, logs won't rotate despite correct config.

2. Step 2: Consider other causes

   Misspelling or wrong path cause errors, but usually logs won't grow if Jenkins stopped.

3. Final Answer:

   The logrotate service is not running or not scheduled -> Option B

4. Quick Check:

   Logrotate must run to rotate logs [OK]

Hint: Ensure logrotate runs regularly to rotate logs [OK]

Common Mistakes:

• Assuming Jenkins must be stopped for rotation
• Ignoring logrotate service status
• Overlooking typos in config file

5. You want to rotate Jenkins logs daily without stopping Jenkins and keep logs for 10 days. Which logrotate config snippet achieves this safely?

hard

A. /var/log/jenkins/jenkins.log {
copytruncate
daily
rotate 10
missingok
notifempty
}

B. /var/log/jenkins/jenkins.log {
delaycompress
weekly
rotate 10
}

C. /var/log/jenkins/jenkins.log {
copytruncate
monthly
rotate 10
}

D. /var/log/jenkins/jenkins.log {
compress
daily
rotate 5
}

Solution

1. Step 1: Identify safe rotation without stopping Jenkins

   copytruncate copies and truncates logs safely without stopping Jenkins.

2. Step 2: Check rotation frequency and retention

   Daily rotation with rotate 10 keeps 10 days of logs. missingok and notifempty handle missing or empty logs safely.

3. Final Answer:

   Config with copytruncate, daily rotation, rotate 10, missingok, notifempty -> Option A

4. Quick Check:

   copytruncate + daily + rotate 10 = safe rotation [OK]

Hint: Use copytruncate for safe daily rotation without stopping Jenkins [OK]

Common Mistakes:

• Using monthly or weekly instead of daily rotation
• Not using copytruncate causing Jenkins stop
• Setting rotate less than 10 days